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Oct-2015

FCC catalyst lowers dry gas and improves yield (TIA)

Trials with BASF’s Boron Based Technology (BBT) catalyst platform demonstrated higher flexibility and profitability for refiners processing resid feeds by minimising the negative impact of contaminant metals and providing higher yields of valuable hydrocarbon products.

Alexis shackleford
BASF Corporation, Catalysts Division

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Article Summary

Fluidised catalytic cracking (FCC) units that process resid feeds face a number of unique challenges. Resid feeds contain contaminant metals including nickel (Ni), vanadium (V), and iron (Fe) that catalyse a variety of unwanted secondary reactions in the FCC unit. Even small amounts of these contaminant metals in the feed accumulate on the catalyst, which is a major concern for the refining industry. Nickel, specifically being a highly active dehydrogenation catalyst, significantly increases FCC unit hydrogen (H2) and coke yields. High H2 yield can limit the unit’s wet gas handling capacity and high coke yield lowers the unit profitability. Resid feeds also contain higher amounts of large molecules, aromatics and Conradson carbon residue (CCR) compared to vacuum gas oil (VGO) feeds. Due to these large molecules, optimised catalyst pore structure is critical to convert the heavier material to more valuable products. To deal with these challenges, BASF has developed the new BBT catalyst platform. The first product is Borocat, which is designed for heavy resid and maximum conversion operation.

The BBT platform utilises a Ni-passivating boron compound integrated with optimised pore structure for processing resid feeds. With a high degree of flexibility, the new technology minimises the negative impacts of contaminant metals and provides higher valuable liquid hydrocarbon yields. The boron compound, which is loaded onto a proprietary inorganic support, is introduced into the catalyst to passivate Ni thus reducing H2 and coke yields. The boron technology also has the added benefit of improving light cycle oil (LCO) selectivity by upgrading more slurry to LCO.
One of the commercial trials with Borocat was at the Tamoil Collombey refinery, whose FCC unit processes 100% atmospheric resid feed. The FCC is an R2R design, processing a feed with 0.930 specific gravity (20.7 °API gravity) and 4-6 wt% CCR. The unit uses antimony for Ni passivation and BASF’s Maximum Olefins Additive (ZSM-5 based additive) for enhanced olefins yield. Prior to introducing the new Borocat catalyst, the unit was using BASF’s resid catalyst Fortress, with equilibrium catalyst (e-cat) Ni+V levels typically between 5000-10 000ppm.

With the use of the new Borocat catalyst, the unit was able to lower the catalyst addition slightly from 2.7 to 2.5 kg/MT feed while increasing the e-cat fluidised activity (second order activity) by +1 number. With the higher catalyst activity, the unit decreased riser outlet temperature by 4°C. The unit achieved slightly more conversion (79 wt%) at the new operating conditions. Going into the trial, metals started to rise on the e-cat. Nickel increased from 3500 ppm to 4500 ppm and V increased from 3000 ppm to 3500 ppm. During the metals increase period with Fortress, unit H2 yield increased from 0.13-0.14 wt% to 0.18 wt%. With Borocat at the same metals levels, H2 was reduced back to the base level of 0.13-0.14 wt%, despite having almost 25% higher metals on e-cat. The new Borocat catalyst also showed improved coke selectivity at equivalent metals level. The unit delta coke decreased ~25%, resulting in a significant 25°C decrease in the R2 dense bed temperature. The improved hydrogen selectivity, with lower ROT and lower regenerator temperature, led to a decrease in dry gas of 0.5 wt% (see Figure 1). Borocat also gave improved liquid yields for the unit. The LCO/slurry ratio, which is one measure of the bottoms upgrading ability of the catalyst, increased from 1.0 to 1.5. Slurry yield decreased from 11 wt% to 8 wt%, while LCO increased from 11.5 wt% to 12.5 wt%. The liquefied petroleum gas (LPG) plus gasoline yield increased by ~3 wt%. The improved yields of the unit are a result of the higher LCO selectivity, improved H2 and coke selectivity, and higher catalyst activity.

In summary, BASF’s new BBT catalyst platform offers higher flexibility and profitability to refiners processing resid feeds by minimising the negative impact of contaminant metals and providing higher yields of valuable hydrocarbon products. The performance of the first catalyst from the BBT platform, Borocat, was studied at a European refinery and demonstrated improved H2 and coke selectivity, and overall improved yields for a successful trial.

This short case study originally appeared in PTQ's Technology In Action feature - Q4 2015 issue.
For more information: alexis.shackleford@basf.com


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